Tellurium toning-bath and process of toning photographic elements.



exam ple, by

No Drawing.

To all whom it may oncern e it known that I, Ennuxn R. liomiorn. ofRochester, county of Monroe, State of New York, have invented certainnew and useful Improvements in Tellurium 'loning aths and Processes forToning Photo graphic Elements; and I do hereby declare the following tobe a full, clear, and exact description of the same.

y invention relates to photography and more particularly to toning bathsand the process of toning photographic prints and as for its object theprovision of a satisfactory and easily manipulated toning bath and aprocess for toning whereby a rich brown or sepia color effect may beobtained which is highly pleasing to the eye. To this and other ends, aswill appear from the following disclosure, my invention resides in thecombination of nuts and the steps of the process as set forth in theappended claims.

In the practice of my invention, I utilize a toning bath fortransforming the ordinary lack and white tones of a silver image into abrown or sepia color efi'ect which comprises an acid solution containinga compound of tellurium and which furnishes a molecular compound or anion in solution capable of reacting with silver to form an image whichis insoluble in water or preferably insoluble in the toning bath.

solution of a telluriuin halid, preferably a chlorid of t'etravah-nttellurium, in a hydrogen halid acid is found to be well suited for thispurpose and to produce excellent sepia tones. While an excess of acid inthe solution is preferred, there should be utilized sutiicicnt acid tooppose any tendency toward complete hydrolysis and mainsalt in solutionto carry on the toning, reaction. A bath involving the halid oftellurium may be formed, for dissolving tellurium dioxid TeO inhydrochloric acid, an excess of the latter being present. Thetetravalent tellurium salt, tellurium chlorid (Tech), is probablypresent in the bath and servesas the reagent which forms with ima e acompound that is substantially insolu le in the toning bath.

If other element, such as plate film or paper bearing a silver imagewhiehhas been developed, fixed and washed in the usual man-Speeification of Letters Patent. Application filed April 5, 1916.

an ordinary photographic print or tatl Patented July 23, 1918. SerialNo. 89,017.

nor. is immersed in the telluriuin bntluthe photographic print or otherelement changes from its former approximately black or silver color to asepia tone, probably due to the formation of a compound of silver andtellurium according to tion:

in which X represents the halogen or other ion that reacts with thesilver to form the insoluble compound. Both the resultant pr ducts inthe above reaction are insoluble in the bath, but the silver-telluriumcompound due to its predominating furnishes the tone to the image, theother salt merely degrading the color eifect some what.

Since the bath should be free from injurious substances or those whichtend to attack the gelatin or which have a tendency to dissolve thesilver before it has had time to tone, or to dissolve thesilvertelluriuin compound after the toning has taken place, I preferablyutilize dilute hydrochloric acid as the solvent for the telluriuincompound. due to the slowness of reaction of the tellurium chlorid inhydrochloric acid on the silver image, I find it desirable that the bathcontain an adagent to accelerate the velocity of the toning process.Also, it is found that after the toning has taken place and the print isbeing washed, the extreme dilution of the solution of the telluriumcompound present in the pores of the gelatin tends to form a precipitateoi the oxid or hydrated oxid on the print, although acid has been usedin the initial solution. This deposit, at first white in color, tends tobe gradually reduced by the gelatin to form a black deposit over theentire print. To overcome the formation of an undesirable precipitantand to accelerate the reaction velocity, I add to the tellurinm halidbath a halid of an alkali metal, preferably a bromid. Advantageousresults are obtained by using sodium chlorid and potassium bromid, Byutilizin t, these salts it is possible to dilute the toning bathindefinitely or to wash the print completely without danger of precipi'on of an undesirable tellurium compound because of hydrolysis.

s a' specific example, the following ingredients and proportion measuredin grams the following equaa mixture of and cubic centimeters may been'iployed for use with one well known brand of pliolographic silveemulsion paper, although. of course, they may be varied to accord withthe character of any other kind of photographic element; that is to besepia toned:

in. Tel) l'lCl (concentrated.) J in. NaUl. in. Kllr. ater to make 100cc.

'hile the chemical structure of the compounds present in the telluriumbath and the exact nature of their reactions is immaterial, so far asthe character and operation of my invent ion is concerned, there maypossibly be present in the acid bath containinp, the alkali metal lialidsalts, a double salt of the type Na. ,'lellr,,; however, the reactionmay be represented as proceeding according to the following simpleformula, tellurium clilorid being considered the reactive agent:

Tcul l lKlir-ttiAg:

Ae 'l'elAgBr+ thCl By using baths of the above spccilic natures. a sepiatone is obtained, no further chemical treatment oi the print beingiieces sai'v. However, it is preferable to add anotlii-r step to theprocess to obtain a deeper and richer ctl'ect and to regain the densityof the original print, which was slightly reduced by the bleachingaction of tlie tellurium bath. l, accordingly, wash the print,preferably in running, water, for a sutlicient time to remove the acidsolution and then treat. the image with a Nafi solution, pref erably atwo per cent. solution of sodium sullid crystals. The result of thisstep is probably to transform the white or light colored silver broiiiidor silver clilorid, which otherwise would tend to change to apliotobroniid or photochlorid upon exposure ol the photographic element;to light, into the dark colored and more permanent silver sulfid, theprint being given thereby substantially the same density as wasoriginally present.

The operation of my process is simple. An ordinary silver print, forexample, after the usual developing, lining and washing op erations, isimmersed in a tray containing my tellurium toning bath or otherwisetreated therewith for about two minutes or until the visible change inthe print is complete, preferably while the tray is rocked or thesolution otherwise stirred. It is inadvisable to prolong tlie treatmentol the print with the tellurium solution after a. satisfactory result isobtained, as the color values ma be disadvaiitageousl alli-cteilthereby. The print; may then be washed and dried, or, if the sodiumsullid treatment is desired, it; is

'ver tellurium. and

washed preferably until ll'it" acid has been substantially eliminatedand then treated with a two per cent. aqueous solution of sodium suliidto darken and intensify the print. When the color change has takenplace, the print is washed and dried in the usual manner to complete theprocess.

Ilaviing described my invention, I claim:

1. A photographic toning bath for silver images comprising a telluriumcompound in an acid solution, said bath being capable of converting thesilver image into one which is insoluble therein.

2. 'A photographic toning solution for silver images comprising acompound of tellurium and an acid, said solution being capablc offorming a compound containing sila silver salt which are insoluble insaid bath.

A photographic toning solution for silver images containing a compound ol' tetravalent tellurium and an acid, said solution comprising asubstance which is capable of forming a compound containing silver,tellu rium, and a silver salt that are insoluble in said solution.

4. A photographic toning bath for silver images comprising a telluriumcompound,

water, and an acid which will prevent precipitation ot' a telluriumcompound and will not injuriously attack the silver image.

5. A photographic sepia toning ath comprising a tellurium salt in asolution cont-aining a hydrogen lialid acid.

(3. A photog; aphic sepia toning bath comprising a tellurium clilorid ina solution acidilied only with hydrochloric acid.

7. A photographic toning bath comprising a solution containing atellurium lialid and an accelerating agent.

8. A photographic toning bath couiprising a solution of a tellurium saltand an agent capable of retarding hydrolysis and precipitation of atellurium compound upon dilution with water.

9. A photographic sepia toning bath cor prising a tellurium chlorid in asoluiii...

containing hydrochloric acid in excess and a lialid salt.

10. photographic sepia toning bath omprising a tellurium compound in asolution containing hydrochloric ac d in excess, sodium chlorid andpotassium broinid.

11. A j photographic toning bath comprising tellurium chlorid,hydrochloric acid in excess, sodium chlorid and potassium bro-. mid.

12. The process of sepia toning a photographic silver image comprisingthe step of treating the silver image with an acid solution containing atellurium salt.

13. The process of toning a photographic silver image comprisin the stepor changing the color of the silver image by ti ating it ll a. solutionof tellurium cliloricl dissolved in an excess of hydrochloric acid andproducing a silver compound that is insoluble in Water.

14. The process of toning a photographic silver image comprising thesteps of. treating said image with a solution of a tellnrium salt toproduce a given tone; and mo lifying said tone by treatment with asullid solution.

15. The process of toning a photographic silver image comprising thesteps of treating the image with an acid solution of a tellurium salt toproduce a given sepia tone and treating with sodium sulfid to modifysaid tone.

16. The process of sepia toning a photographic silver image comprisingthe steps A of bleaching and sepia toning the silver image with asolution containing a tellurium halid and intensifying and modifyii gthe tone of the image by treating with a sodium sulfid solution.

17. The process of toning a photo raphic silver image comprising thesteps 0. treating said image with an aqueous solution of telluriumClllOX'lll, hydrochloric acid, sodium chlorid and iotassium bromid andthereby bleaching am toning the image, and intensifying and modifyingthe tone of the image by means of an aqueous sodium sulfid solution.

In witness whereof I affix my signature this 1st day of April, 1916 inthe presence of two witnesses.

EDMUND R. BULLOCK.

Witnesses:

ALONZO S. MCDANIEL, G. C. COOKE.

